mod_proxy_fcgi always uses the error pages of the backend server, even when "ProxyErrorOverride on" is specified.

Configuration:

    <Location /test/>
        ProxyPass fcgi://127.0.0.1:9000/www/php-ssl/
        ProxyErrorOverride on
    </Location>

If the end user requests

http://server-name/test/this-does-not-exist

they should get an error page from httpd (either the default one, or the one configured in an "ErrorDocument 404" directive).  Instead, the user gets the error page generated by the backend server.


Additional information:

# /usr/sbin/httpd -V
Server version: Apache/2.3.12-dev (Unix)
Server built:   Mar 10 2011 16:36:16
Server's Module Magic Number: 20110203:2
Server loaded:  APR 1.4.2, APR-UTIL 1.3.10
Compiled using: APR 1.4.2, APR-UTIL 1.3.10
Architecture:   64-bit
Server MPM:     prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APR_HAS_SENDFILE
 -D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_SYSVSEM_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=256
 -D HTTPD_ROOT="/etc/httpd"
 -D SUEXEC_BIN="/usr/sbin/suexec"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="conf/mime.types"
 -D SERVER_CONFIG_FILE="conf/httpd.conf"

php-fpm from PHP 5.3.6-dev
Fedora 14 64-bit (fully patched)
gcc 4.5.1

httpd custom built from svn trunk with:

./configure --prefix=/etc/httpd --exec-prefix=/usr --bindir=/usr/bin
--sbindir=/usr/sbin --mandir=/usr/share/man --libdir=/usr/lib64
--sysconfdir=/etc/httpd/conf --includedir=/usr/include/httpd
--libexecdir=/usr/lib64/httpd/modules --datadir=/var/www
--with-installbuilddir=/usr/lib64/httpd/build --with-mpm=prefork
--with-apr=/usr --with-apr-util=/usr --enable-suexec --with-suexec
--with-suexec-caller=apache --with-suexec-docroot=/var/www
--with-suexec-logfile=/var/log/httpd/suexec.log
--with-suexec-bin=/usr/sbin/suexec --with-suexec-uidmin=500
--with-suexec-gidmin=100 --enable-pie --with-pcre --enable-mods-shared=all
--enable-ssl --with-ssl --enable-distcache --enable-proxy --enable-cache
--enable-disk-cache --enable-socache-dc --enable-ldap --enable-authnz-ldap
--enable-cgid --enable-authn-anon --enable-authn-alias --enable-session
--enable-session-cookie --enable-session-dbd --enable-lua --enable-dav-lock
--disable-imagemap